Information
The net.ipv4.ip_forward and net.ipv6.conf.all.forwarding flags are used to tell the system whether it can forward packets or not.
Rationale:
Setting the flags to 0 ensures that a system with multiple interfaces (for example, a hard proxy), will never be able to forward packets, and therefore, never serve as a router.
Solution
Set the following parameter in /etc/sysctl.conf or a /etc/sysctl.d/* file:
net.ipv4.ip_forward = 0
net.ipv6.conf.all.forwarding = 0
Run the following commands to set the active kernel parameters:
# sysctl -w net.ipv4.ip_forward=0
# sysctl -w net.ipv6.conf.all.forwarding=0
# sysctl -w net.ipv4.route.flush=1
# sysctl -w net.ipv6.route.flush=1
Item Details
Category: CONFIGURATION MANAGEMENT, SYSTEM AND SERVICES ACQUISITION
References: 800-53|CM-2, 800-53|CM-6, 800-53|CM-7, 800-53|CM-7(1), 800-53|CM-9, 800-53|SA-3, 800-53|SA-8, 800-53|SA-10, CSCv6|3, CSCv6|11, CSCv7|5.1
Control ID: 165cfd00d5ccd0d731e0baead8797dd4ad46e58a81e20b369bf4017e36c2d816